Groundwater quality variation in Kalpitiya Peninsula- Sri Lanka

Abstract

This study presents an evaluation of ground water quality in a unique coastal ecosystem Kalpitiya, which is a low-lying peninsula in north-western coast of Sri Lanka. This peninsula appears as a narrow strip of land which has an area of 160sq km and geographically it is bordered by the Indian Ocean from one side and Puttalam lagoon from inland. One salient feature of this landscape is that it comprises mainly of sand dunes. In addition, coconut and other cultivation and scrub land dominate in the area. Ground water is the main source of water supply for domestic and agricultural needs. The main impact on ground water is believed to be from the sea water intrusion and agricultural activities. Objective of this study was to evaluate the physical quality of ground water during the dry season. Field investigations were carried out for 3 months (December 2013 to February 2014- dry season) and water samples collected from a network of dug wells were analyzed for pH, Electrical conductivity (EC), Temperature and Salinity. ArcGIS 10 package was used to identify the spatial distribution of ground water characteristics. Inverse distance weighted (IDW) technique of Spatial analysis tool was used in ArcGIS 10 version and maps were developed. The study revealed that the range for the pH values was recorded between 6.8 and 8.5 mg/L. Average Electrical Conductivity (EC) was recorded between 103 µS/cm – 33016 µS/cm and average Salinity was recorded between recorded 0.1ppt - 31.40ppt during the sampling period. Talavila area, average EC was recorded as 33016µS/cm and salinity was 31.4 ppt. pH of water too was high in that area reaching the highest desirable level in Sri Lankan potable water standards (pH 7.0 – 8.5; SLS 614, 1983). This may be due to the contamination with ammonia based agrochemicals which are used heavily and higher evaporation rates. Electrical Conductivity levels were greater than the 750 µS/cm exceeding Sri Lankan standards. Thus, it is apparent that ground water in the area could not be recommended for domestic consumptions at least during the dry season. Changing climate resulting less rainfall and sea level rise will aggravate the problem.